Astronomers studying a rare interstellar comet have discovered something surprising: it contains unusually large amounts of methanol, a type of alcohol.
The discovery offers a fascinating glimpse into the chemistry of another planetary system and how comets may form beyond our solar neighborhood.
The object, known as Comet 3I/ATLAS, is only the third confirmed visitor from interstellar space ever detected passing through our solar system. Scientists recently used the powerful Atacama Large Millimeter/submillimeter Array (ALMA) in Chile to examine the comet’s chemical makeup as it moved closer to the Sun.
Their observations revealed that the comet is packed with methanol at levels rarely seen in comets from our own solar system.
“Observing 3I/ATLAS is like taking a fingerprint from another solar system,” said Nathan Roth, the study’s lead author and a professor at American University.
By studying the comet’s chemistry, researchers can learn about the conditions where it originally formed. The findings were posted on the arXiv preprint server.
As 3I/ATLAS traveled toward the Sun in late 2025, sunlight warmed its icy surface. This caused frozen gases and dust to escape into space, forming a glowing cloud around the comet called a coma. By analyzing the light coming from this cloud, astronomers were able to identify the molecules present and measure their amounts.
The research team focused on two molecules: methanol and hydrogen cyanide. Both are organic compounds that commonly appear in comets. Methanol is a simple alcohol molecule, while hydrogen cyanide contains nitrogen and is often found in icy bodies across the solar system.
The ALMA observations revealed something unusual. The amount of methanol compared with hydrogen cyanide was extremely high. The researchers measured ratios of about 70 and even 120 during two observation periods. These numbers place 3I/ATLAS among the most methanol-rich comets ever studied.
This unusual chemical mix suggests that the comet formed under very different conditions than most comets that originated in our solar system. Earlier observations using the James Webb Space Telescope had already shown that the comet’s coma contains large amounts of carbon dioxide. The new discovery adds another distinctive feature to the comet’s chemistry.
ALMA’s high-resolution images also allowed scientists to see how these molecules move away from the comet. Hydrogen cyanide appears to come mainly from the comet’s solid core, called the nucleus, which is typical for comets. Methanol behaves differently. It seems to be released both from the nucleus and from tiny ice grains floating in the coma.
These small icy particles act like miniature comets. As they warm up near the Sun, they release methanol gas into space. While similar behavior has been observed in a few comets from our solar system, this is the first time such detailed outgassing has been studied in an interstellar object.
Interstellar visitors like 3I/ATLAS are extremely valuable to scientists because they carry material formed around other stars. By studying them, astronomers can compare how planetary systems form across the galaxy.
So far, only three interstellar objects have been detected: 1I/’Oumuamua, 2I/Borisov, and now 3I/ATLAS. Each one has shown unusual characteristics. As telescopes improve and astronomers discover more of these cosmic travelers, they hope to uncover new clues about how planets, comets, and organic molecules form throughout the universe.
Source: KSR.
